Polyester composition for extrusion blow molded containers with improved aging and drop performance

Abstract

The present invention relates to a polyester resin for extrusion blow molded containers comprising a branched copolymer and fumed silica to improve the aged drop performance said branched copolyester is made from the reaction of purified terephthalic acid or its dimethyl ester, ethylene glycol, bifunctional diacid other than terephthalic acid, diol other than ethylene glycol, and multifunctional compound having a least 3 carboxyl groups, hydroxyl groups and / or ester forming groups thereof, said fumed silica has a particle size of 0.1 to 5 microns and is present at about 100 ppm to about 2,500 ppm based on the weight of said copolyester.

Description

PRIORITY[0001]This application claims the benefit of U.S. Provisional Application 61 / 897,606 filed Oct. 30, 2013.FIELD OF THE INVENTION[0002]This invention relates to polyester polymers, and more particular to polyethylene terephthalate copolyesters containing fillers for use in making transparent extrusion blow molded containers. Such containers are useful for a variety of products such as soft drink bottles, milk jugs and shampoo bottles.BACKGROUND OF THE INVENTION[0003]Aromatic polyesters generally are semi-crystalline and have low melt strength. Containers made from polyethylene terephthalate (PET), with minor amounts of a comonomer, by the injection stretch molding process (ISBM) are the most common transparent container on the market. However the ISBM process is limited to uniform shapes and cannot produce bottles with a handle. Handles are desirable for larger bottles and containers for easy of handling by the consumer. Such larger bottles and containers with handles can be p...

AI Technical Summary

Benefits of technology

[0014]In the broadest sense, the present invention relates to a polyester resin for extrusion blow molded bottles comprising a branched copolymer and fumed silica to improve the aged drop performance.

[0015]In the broadest sense, the polyester resin for improving the aged drop performance of bottles has purified terephthalic acid, ethylene glycol, pentaerythritol and fumed silica.

Problems solved by technology

Aromatic polyesters generally are semi-crystalline and have low melt strength.

However the ISBM process is limited to uniform shapes and cannot produce bottles with a handle.

However a resin with high melt strength, or high melt viscosity at zero shear rate, is too viscous to be extruded in the extruder and pumped through the die without using high temperatures which cause the polymer to degrade and lose its melt viscosity.

The typical PET resins used to ISBM beverage containers are not suitable for extrusion blow molding due to their relatively low intrinsic viscosities (IV≦0.85 dL / g) and high melting points (>245° C.) which gives a low melt strength at the temperatures needed to process them.

In addition during the extrusion blow molding process the molten polyester cannot thermally crystallize otherwise a cloudy container is produced.

These ultra-high IV polyester resins have to be processed at higher temperatures which cause the resin to thermally degrade giving increased yellowness in the container, and a narrow EBM processing window.

Containers made from amorphous copolyesters, when added to the postconsumer PET recycling stream, tend to cause sticking, agglomeration and bridging issues during the drying process.

This makes such EBM PET resins unsuitable for reuse in the post-consumer polyester recycle stream that is used in blends with virgin resins for use in the standard container and bottle ISBM process.

It is well known that amorphous polyesters age with time (A. Bhakkad, E. A. Lofgren and S. A. Jabarin, ANTEC 2000 Conference Proceedings, pages 2019-2023) making containers made from amorphous polyesters more brittle with age (lower impact resistance), and thus more prone to breakage when dropped.

None of these patents discloses the use of these fillers to improve the aging of polyester articles.